question about a file?

[Joe & Penny Goss]

Keith,
Only a guess, but I think that it could have come from several meanings of
the word, and their use in slang to describe how the file looked or worked.
You know the first meaning, the second is any irregular , or counterfeit
thing (these are noun usage's)
Adverbs include abnormal or irregular in size, shape, or proportion.
A bastard file cuts quickly with no finesse as to final shape of the work
thus it is a crude cut file. An irregular cut
It might be considered counterfeit in that no one would consider it a file
because of its rough cut. 
The cutting teeth on the file, when first made by hand, were hardly a nice
even size or shape
as the metal is gouged out to make the cutting teeth of the tool.
Joe Goss
I wondered how a file became known as a "bastard" file.  Anyone have
> a resource or  information concerning the history of this naming, please?
>